Ecology - GCSE Biology AQA

Specification 4.7

Habitat

place where an organism lives

Population

all organisms of a particular species that live in that habitat

Community

All the populations of different species that live together in a habitat

Ecosystem

Interaction of a community of living organisms with the non-living parts of their environments 
Habitat, Population, Community combined with Abiotic and Biotic factors 

Resources that animals need to survive:

Space/territory, food, water and mates

Resources that plants need to survive:

Light, space, water and mineral ions from soil 

Why does competition happen and who does it happen between?

All resources are limited therefore organisms have to compete with each other for them
Competition can happen between both same and different species

Interdependence

All species depend on other species in some way and rely on each other for survival
If something changes, it affects everyone in the community

Biotic Factors

living factors of environment that can affect organisms or shapes ecosystem in any way 

Predation

Competition for resources and habitats

amount of disease

Food availability

Abiotic Factors

Non living factor of environment that affects organisms or shapes ecosystem in any way

Light intensity

temperature

Co2 Concentration

Moisture levels

Intensity/direction of wind

pH/mineral content of soil

Interspecific Competition

competition between individuals of different species

Intraspecific competition

Competition between individuals of the same species

3 categories of adaptations in an organism 

Structural, Behavioural, Functional

Structural adaptations

Physical Features that are seen

Structural Adaptations Examples

Seals have rounded shapes for cold environment therefore they have low surface area to volume ration which helps them to conserve body heat

Desert Fox/animals - have big ears to cool down - small pupils to protect eyes from sun damage

Seals are grey to help camouflage against predators 

Behavioural Adaptations

Way organism behaves or acts

Behavioural Adaptation Examples 

Migration to warmer countries during winter

Bears hibernate in the winter to conserve energy and body heat 

Desert Animals are Nocturnal as it is colder at night

Functional Adaptations

Processes inside an organism

Functional Adaptation Examples

Desert animals sweat very little and have concentrated urine to limit water loss 
Camels have humps which have fat inside which can be broken down into water 

Extremophiles

Microorganisms (archaea/bacteria) adapted to live in extreme environments and pump out digestive enzymes

Extremophiles Examples

Thermofiles - Living in hot temperature like hot springs
Halophiles - Living in high salt concentration areas like a salt water lake
Acidofiles - acid resistant
Radiophiles - radioactive resistance

Extremophiles uses

Thermofiles - used in washing detergent as they can withstand the high temperature in washing machines

Acidophiles - used to make cheese as they pump out H+ Ions

Halophiles - used for making soy sauce as they can withstand high salt concentrations

Radiophiles - used to clean up radioactive areas

Bacteria in intestines are mostly anaerobic 

Bergmann theory

Larger surface area to volume ratio in cold climates
Lower surface area to volume ratio in warm climates

Allen theory

Extremities longer in hotter environments so more heat can be lost

Hot environment adaptations

Nocturnal, exoskeleton, small pupils, large feet

Cold environment adaptations

Thick fur and layer of fat under skin - insulation 

Few blood vessels - less heat lost

Huddling to preserve body heat 

Predator adaptations

Slit pupils - focus

High speed sprinting so more fast twitch muscle fibres

Prey adaptations

Rectangular vision to see all round for predators

More stamina to run away

Food chain

what gets eaten by what in ecosystem

Producers

(green plants) photosynthesise to produce their own food - autotrophs

All the energy in the food chain comes from the producers who get their energy from the sun

Primary consumers

eat producers and the biomass from the producers is transferred to the primary consumers - usually herbivores

Secondary consumers

predators/carnivores that eat primary consumers

Tertiary Consumers

Carnivores that eat secondary Consumers

Biomass

Biological molecules incorporated into plants

Why is most energy lost when passed up food chain? 

Not all biomass is digestible (egested through faeces)

Movement of Organisms uses up energy 

Keeping organism warm, respiration and processes inside the body uses up energy and thermal energy is lost to the surroundings 

Predator - Prey Cycle

• Out of phase 

• When there are lots of mice, lots of food for owls, owl’s population goes up and the mice population goes down 

• Fewer mice, less food for owls, owl population goes down and mice population goes back up 

• Cycle repeats - takes long time for population to increase and decrease

Excretion

getting rid of waste produced in metabolic reactions: urine

Egestion

never part of body, passes through and is removed: Faeces

Plant adaptations Example

spreading seeds far so not in competition with their offspring

Artic Plants adaptations Examples

dark green leaves

evergreen trees

pinecones

needle leaves

chemicals

thick bark

Tropical rainforests plant adaptation examples

• Holes in leaves

• Carnivorous plants

• Tall trees

• Wide roots/thick base

Cactus/dry Plant adaptation examples

• Large vascular bundles

• Water is acidic or alkali

• Far stretching roots

• Thorns, hairs and spikes

Abundance

number of individual organisms species in a given area

Distribution

where organisms are found within a given area

Subsets

used to make predictions about the whole population

2 Methods for Sampling

• Quadrats - to measure abundance

• Transects - to measure how distribution changes

Quadrats

Sample areas must be chosen at random through a random number generator

Placed at regular intervals along a transect

Transects 

Laid out in straight lines 

Water Cycle

Energy from sun causes some water to evaporate to water vapour 

Water vapour accumulates and condenses into clouds

Water will fall back down to earth through precipitation

Seeps into soil, falls to rivers, used by plants - cycle then repeats

Passes through animals and plants

released by plants by transpiration and loss by both animals and plants through decay, urine, sweat and faeces

Where is Carbon Primarily?

in air, plants, (biological molecules), soil (bacteria)

Carbon Cycle 

Photosynthesis: plants take in CO2 from air 

Carbon in plants can either be released back into air (respiration) or passed into animals who eat the plants 

When plants + animals die, organisms decay by microorganisms in soil, break down into small pieces until all carbon is released.

During microbial respiration, if organisms decayed in anaerobic conditions, may be converted into fossil fuels which are burned by humans, releasing carbon dioxide

Burning plants for fuel and energy also releases carbon dioxide

Decomposition

process where dead organic matter is broken down into simpler organic or inorganic substances - such as carbon dioxide, water, simple sugars, and minerals
Recycles elements throughout an ecosystem

Microorganism digestion 

Happens outside cells 

secrete enzymes that break down the chemicals

absorb some nutrients they need and leave the rest in soil

Amino acids broken down to form ammonia form ammonium ions during deamination

Decomposers optimum conditions

Cells dry out easily therefore thrive in warm and moist conditions

Need plenty of oxygen for respiration

Grow under material they are decaying 

Who is decomposition carried out by?

Carried out by detritus feeders which are small animals like worms or woodlice that feed on dead organic matters

Carried out by decomposers which are microorganisms: bacteria or fungi

Factors affecting rate of decomposition

Oxygen Availability - higher oxygen - more aerobic respiration - more energy available - faster growth and decomposition

Temperature - higher temperature - particles have more kinetic energy - enzymes closer to optimum temperature - higher rate of reactions - more decomposition

If temperature becomes too high - enzymes denature - lower rate of decay

Water content - decomposers need water to survive - rate of decomposition increases in moist conditions

If soil becomes water logged - oxygen levels will fall - there will be lower rate of decomposition

Compost

mixture of decayed organic material - used to fertilise and improve soil

Prepped by leaving dead plant waste in ideal (oxygen, water, moist) conditions until mostly decomposed - provides nutrients for plants

Anaerobic respiration of decomposers 

Some decomposing microorganisms can break down organic material anaerobically (anaerobic decay) producing a mixture of gases called biogas - methane is produced
When methane combusted - releases lots of energy used for cooking, heating and electricity 

Biogas generators

Large containers in which animal or plant waste left to decay anaerobically - no oxygen otherwise not as much methane produced

Once biogas removed from tank - sludgy material leftover - high density of useful minerals - spread on field like fertilisers 

Biodiversity

variety of different species on earth or within ecosystem - important

Advantages of Biodiversity

Safer ecosystem as there are many relationships other species can rely on
Some species act as pollinators or fruits
More than half of new medical drugs are derived from living organisms
Humans thrive off high biodiversity

How do humans damage environment and reduce biodiversity?

Population growth - individuals have higher standards of living - consumers: phones, clothes, cars 

More raw materials and energy needed - used faster than can be replaced

Lots of waste produced from bodies and industrial processes (toxic chemicals and sulphur dioxide) which gets into water, land and air - directly harming organisms and can cause acid rain 

Pollution releases greenhouse gases into the air which contributes to global warming

Climate change, deforestation, dumping waste, reduces biodiversity and damages ecosystem

Ways to improve biodiversity: Breeding programs

Breeding programs for endangered species with chance they will go extinct - build up numbers to reintroduce to wild - join existing population or form new ones

• Breeding in captivity 

• Unless natural habitat is safe, population will decline again therefore we can create protected areas and regenerate rare habitats like mangrove and coral reefs

Ways to improve biodiversity: Farming + Deforestation

Governments can introduce new laws and pay farmers for doing right things

Government can set quotas on deforestation and how much Co2 can be released by businesses 

Individuals can recycle and buy less junk so less waste goes to landfill sights - More land left undamaged, fewer toxic chemicals get into environment

Field Margins and Hedgerows 

Field margins - strip around field where anything can grow
Hedgerows - Act as border 
Increases biodiversity by providing different habitats and food sources where different species can live

Issues and Challenges

Money - protecting biodiversity is expensive and individuals, companies and government overlook how they benefit from high biodiversity and spend money elsewhere
Maintaining current standard of living requires damage to environment
Fertilisers and pesticides used to grow enough food for everyone - mines for rare metals for phones and computers

Why do developing countries rely on the environment for their livelihood?

Cutting down forests to build homes, cook, and get land to grow crops

The Greenhouse Effect

Sun’s heat energy passes thorough atmosphere into earth in the form of light rays

some energy is absorbed and heats up ground

most reemitted or reflected back into atmosphere

some makes it to space but most hit particles of gas in atmosphere which absorb all of the energy and after short delay, particles then remit energy in random directions

some to space, some to earth

most energy collides with other gas particles

happens over again

heat energy stays closer to earth and keeps it warm and at a stable temperature

Happens with green house gases - Carbon dioxide, methane and water

As gases accumulate - greenhouse effect gets stronger, earth warms up

Climate

long term weather patterns

Effects of Global Warming

Rare weather events get more common and severe

Sea levels rise as the higher temperature causes ice to melt and it flows into ocean

As water warms up, it expands causing volume to increase causing sea level to rise

Causes seasonal flooding - submersion of entire islands and coastal towns

General impact - some species may not be able to survive - some might adapt to new conditions or migrate to other regions - lots can’t adapt or migrate fast enough - biodiversity is likely to fall dramatically

Deforestation

happens to clear land for farming, to raise cattle and grow food for cattle as well as make room for new infrastructure

also used to grow crops used for biofuels (plant based fuels we can burn)

Also used for logging (getting wood) which is used to build things or for fuel 

Deforestation happens a lot in tropical regions (e.g rainforests)

Main Problems with Deforestation

less photosynthesis as there will be less trees to take CO2 from the atmosphere therefore more carbon dioxide will be left in the atmosphere which contributes to global warming

Burning forests releases all the carbon that trees were holding, as carbon dioxide - causes smoke that can suffocate animals and pollute towns and contributes to global warming

Habitats are destroyed - reducing biodiversity in area - species become extinct

Peat Bogs

Areas of land where soil is acidic and waterlogged  - microorganisms which help to decay plants can’t survive (acidic water stops air from getting in soil therefore there is not enough oxygen for aerobic respiration
The partially rotten plants build up and form peat
Carbon gets stored in peat as it never gets released from decay
Reduces global warming

Destroying Peat Bogs

After drained to be used as farmland, oxygen comes back due to the water being removed therefore decomposer microorganisms come back and decompose the peat - all the stored carbon is released as carbon dioxide  

Peat burned as fuel or used as compost in gardens 

Destroys habitats - reducing biodiversity and can lead to extinction of species

Trophic levels 

Different levels within a food chain}
Trophic level 1 - always a producer - photosynthesise to create own food
Trophic level 2 - primary consumer (herbivores) 
Trophic level 3 - secondary consumers (Carnivores/Omnivores)
Trophic level 4 - tertiary consumer (Carnivores)
Every time trophic level goes up, some energy is lost therefore there is not enough energy to sustain organisms at a higher trophic level  10 percent of energy is passed on per level

Pyramids of Biomass

show the biomass of each trophic level in a food chain
Bars get smaller up the pyramid
biomass - mass of living organisms
Total mass of the organisms in each level is decreasing - every time one organism is consumed by another - most of the biomass and energy is either lost or used 

Overfishing solutions

Fish farms: large enclosures or tanks designed to provide controlled environments for the growth of fish for humans consumption - allows fish stocks to recover

Opting for fish soured from sustainable fisheries - helps maintain fish stock

Increasing size of fishing nets, enabling younger fish to escape while adults are caught - allow young fish to escape and grow and reproduce - maintaining fish population and contribution to overall sustainability 

Fishing quotas - setting limits on amount of fish that can be caught - help maintain balanced ecosystem and ensure long term viability and sustainability of fish stocks

Food Security 

All people able to access enough safe and nutritious food to meet the requirements for a healthy life in ways the planet can sustain into future

Factors Affecting Food Security

rising population - more people to feed

Diets changing when countries become wealthier - food often transported across world and more meat being consumed - less efficient to produce meat

New pest and pathogens - kill stock and crops - famine

Environmental changes - higher temperature - reduced rain and decreased food yields

Agricultural inputs (fuels and fertilisers) are expensive - food become more expensive

War and conflict - disrupted production and transport of food - food price rises - can cause famine

Mycoprotein

Protein by fungi and can make high protein meat substitutes

Made by a fungus called fusarium when grown in aerobic conditions in glucose syrup as food allow Fungus to respire

Made in Large Vat fermenters that are kept at an optimum pH and temperature for Fusarium to grow

Use water jackets to maintain a constant temperature

Paddle allows reaction mixture to remain aerated

Fungus multiplies within fermenter and is then harvested and purified to produce mycoprotein

Efficiency of Food production

Restricting energy transfer of animals by limiting movement, controlling environment temperature and giving more food - ethical objections 

Global food production

Can be increased by clearing forests and other land for agriculture - application of fertilisers, pesticides and herbicides

Genetically Modified Crops

Crops can be GMed to contain a gene from a bacterium that produces poison that kills insects, making them pest resistant and improving crop yields
Crops can be GMed to make them resistant to Herbicides so only weeds around them die when they are sprayed with herbicides
Crops can be GMed to produce additional vitamins and improve nutritional value, e.g: Golden rice contains chemical that is turned into Vitamin A in the body which can help prevent deficiency diseases in certain areas of the world
Crops can be GMed to be drought resistant, improving yields

Genetic Modification of Bacteria to produce Human insulin

Bacteria plasmid containing the insulin gene is placed into a bacterial cell which is placed into a fermenter to reproduce in large quantities
Insulin is extracted and purified - can be used to treat diabetes